The Ultrafast Nonlinear Optics (UNO) group focuses on nonlinear optics with ultrafast laser pulses on a femtosecond time scale.
About the group
In our group we work with efficient frequency conversion of ultrashort pulses, and seek to discover novel compression methods for generating even shorter pulses than those delivered by commercial laser systems. In particular, nonlinear optical pulses (solitons) generated in standard nonlinear crystals using cascading (phase-mismatched) frequency conversion processes are exploited to efficiently compress longer pulses towards the single cycle pulse duration limit. Mixing of ultrafast pulses in nonlinear media allows for generating energetic ultra-short few-cycle pulses at longer (mid-IR, 2.5-10 micron) and shorter (visible, 0.35-0.75 microns, upper UV, 0.2-0.35 microns) wavelengths.
We work with both state-of-the-art solid state lasers as well as the more compact and rugged fiber laser systems, and our activities are both theoretical and experimental. The overall aim is to have an accessible source of few-cycle pulses anywhere in the optical spectrum.
In the coming years we have particular focus on visible and mid-IR pulses. Such pulses can be used in a broad range of research fields for ultrafast multi-color spectroscopy, coherent excitation and probing of vibrational modes, and ultimately for controlling phase transitions in strongly correlated systems. This could lead to discovery of entirely new properties of matter. We will also expand our focus from purely bulk optics (using high-energy pulses) to also include waveguide optics (using low-energy pulses), which is interesting because the pulses originate from a much more compact laser and the low pulse energies are favorable for fragile biological samples (e.g. for performing nano-laser surgery inside living cells).
First theoretical explanation of the nonlocal nature of ultrafast cascaded nonlinearities (Bache et al. OL 2007
First theoretical prediction of optical Cherenkov radiation in ultra-fast cascaded second-harmonic generation (Bache et al. PRA 2010)
First experimental observation of filament-free soliton-induced
octave-spanning supercontinuum using nonresonant defocusing cascaded nonlinearities (Zhou et al. PRL 2012
First noncritical (type 0) soliton compression experiment with defocusing cascaded nonlinearities (Zhou et al. PRL 2012
First experimental observation of resonant nonlocal response with defocusing cascaded nonlinearities (Zhou et al. PRA 2014)